Angle Bar Research Articles

ON THE LOSS OF STABILITY AND POSTCRITICAL EQUILIBRIUM OF COMPRESSED THIN-WALLED ANGLE BARS

Angle bars in compression are quite common in building and transport structures. However, the peculiarities of their behavior during the loss of stability and in supercritical equilibrium have not been sufficiently studied even within the limits of elastic deformations. The paper shows solutions for the stability of symmetric and asymmetric rods with an angle profile. The development of post-critical deformations is shown. The features of the behavior of the rods, obeying the hypotheses of V.Z. Vlasov.

Stress and displacement analysis of powder packaging machine of capacity 2,600 pcs/hours

This study aims are to analyze stress and displacement using Finite Element Method (FEM) of the three components design of powder packaging machine. The safety factor (SF) is calculated to compare with the design acceptance criteria, more than two. The frame is made of ASTM A36 steel angle bar, while the camshaft and sealer sleeve of AISI 1018. Steel angle bar widths of 40x40 (mm) and 50x50 (mm) with a thickness of 3,4,5 (mm) use for the frame design variant. The diameters of the camshaft design variants are 0.75”, 1”, and 1.25”. Then, the sealer sleeve variant utilizes thicknesses of 10, 12, and 14 (mm). Loading assumption during adverse operating conditions, such as when there is an obstacle or jam. Through the finite element method results, increasing the thickness of the frame also the sealer sleeve, and increasing the diameter of the camshaft, produced a decrease in the value of von mises stress and displacement. The safety factor for all variants of frame thickness was more than two, indicating that all designs were safe and acceptable. Nevertheless, there is one design failure on the camshaft and sealer sleeve because the SF value is less than two.

Material consumption optimization of a welded rafter truss made of angle profiles

Welded rafter trusses are widely used in civil engineering due to the optimal combination of high technological effectiveness and ability to operate under various force scenarios. However nowadays an important role in the construction of long-span building structures is played by saving materials, and consumption optimization. This paper reports on the study of 18000 × 3600 mm rectangular welded rafter truss, made of angle profiles with different shelf lengths but the same wall thickness. The method of computer simulation experiment has been applied using ANSYS Workbench 14.5 software package. The scheme of basing, typical for such construction, was accepted: basing on the extreme nodes of the bottom chord and static loading on two intermediate nodes on the top chord. The parameters of the stress-strain state in the structural elements and in places of their connection from the loading start to the onset of the limit state have been identified. It has been found that according to the ratio of material capacity and durability of the structure, the highest indicators are provided by the truss with angle bars of 120x120x10 mm. The research technique accepted in the paper and the obtained results can be used in the design of welded truss construction and in assessing the strength of existing trusses for the purpose of their reconstruction and strengthening.

Construction of surrogate models for predicting the buckling strength of stiffened panels through DoE and RSM methods

PurposeExperimental mid/large scale testing of ship-like stiffened panels in compression is a quite expensive exercise that is not standard. Numerical simulations are preferred instead. Because of being relatively inexpensive (cost and time wise), most authors perform an exhaustive design space exploration arriving at a significant number of runs. This work demonstrates that the buckling response with respect to the nondimensional slenderness ratios may well be fitted with nine runs per stiffener geometry.Design/methodology/approachEfficient derivation of buckling strength formulas for stiffened panels through the employment of design of experiments (DoE) and response surface methodology (RSM) combined with numerical nonlinear experimentation over the entire range of practical geometries.FindingsThe surrogate model developed for T-bar stiffeners predicts accurately enough the ultimate stress in the practical design area, while the surrogate models for angle bars and flat bars demonstrate difference between 10 and 30% from common structural rules (CSR).Originality/valueTo the authors' best knowledge, the statistical-based formal and rigorous approach of DoE and RSM to obtaining buckling surfaces for stiffened panels is performed for the first time. The number of required observations per stiffener type has not been addressed yet as each work selects its own sampling scheme without formal reasoning. This work comes to frame the number of observations for efficient surrogate model building.

Efficient and timely downstream passage solutions for European silver eels at hydropower dams

The European eel population is critically endangered due to a multitude of human-induced factors such as habitat fragmentation, parasites, fishing, and climate change. In freshwater, downstream migrating silver eels encountering hydroelectric plants often suffer substantial delays and increased mortality from trash-rack impingement and turbine-induced mortality. Downstream passage problems can be ameliorated by implementing different types of downstream passage solutions that show variable but promising results for salmonids, but their performance for silver eels remains largely unknown. To address these knowledge gaps, radio telemetry was used to monitor the downstream migration of silver eels during 2 years past a hydroelectric plant recently equipped with two new fish passage solutions, consisting of an angled bar rack with a full-depth bypass, and a nature-like fishway. No tagged eels passed through the turbines, but bypassed the dam evenly between the two passage solutions, resulting in a 95% impediment passage efficiency and a median passage time of 1 h. Movement patterns and route selection were associated with variation in discharge and most individuals approached both passage solutions before passing, resulting in route-specific efficiencies of 69% for the angled rack and bypass, and 46% for the nature-like fishway. We conclude that the combination of a new bypass, paired with an angled rack, and a large nature-like fishway provided downstream migrating silver eels with a highly effective combination of passage solutions, with high impediment passage success and relatively low passage times.

Experimental study of fish-friendly angled bar racks with horizontal bars

This paper presents an experimental study of angled fish-friendly bar racks with horizontal bars, using a physical model in an open channel. Head losses are investigated for two bar shapes, three ratios between bar spacing and bar thickness and four angles of orientation of the racks. The Froude and bar-Reynolds numbers were respectively 0.275 and 3600. The head loss coefficients decrease as the blockage ratio and the angle of orientation of the rack decrease. They are well predicted by a formula produced previously for an inclined rack, with some adaptations. Velocity fields are characterized upstream and downstream of the racks, showing no effect of the angle of orientation and no heterogeneity over channel width. Consequently, the normal and tangential components of the velocity along the rack are in agreement with the theoretical values given by angular decomposition. These results serve to assess the compliance with biological criteria to avoid impingement risks and guide fish towards a bypass.

A study of bearing capacity of reinforced masonry beams with GFRP reinforcement

This article presents the results of experimental researches of bearing capacity and deformability of reinforced masonry beams with combined reinforcement. This study was carried out in the zone of maximum bending moment. The reinforcement A400C and A1000 were used for experimental samples. The combined action of ceramic masonry and reinforcement was ensured at the expense of a cement-sand grout in the joints of masonry and vertical reinforcing meshes in support zones of beams, which were welded to angle bars. Besides that, there was carried out a comparison of the results of experimental researches with calculated values by the active standards of Ukraine. This comparison permits to determine the expediency of the use of the existing design procedure of bearing capacity of reinforced masonry structures with combined double reinforcement. Finally, this scientific work has also presented the conclusions about the possibility of the efficient design of reinforced masonry structures in the effective area of normal forces.

ЩОДО ПИТАННЯ ПРО РАЦІОНАЛЬНУ ФОРМУ ПРЕСОВАНОГО БУЛЬБОКОСИНЦЯ

In airplane building and helicopter engineering a bulb angle bar  an angle bar with a bulb at the end of a wall are widespread. They are better than a simple angle bar, since they have higher critical stresses under compression more than the proportionality limit. They are better than T bar, as T bar are fastened with two rows of rivets, which impairs tightness. Bulb angle bar are better than Z bar. The latter are higher, which reduces the structural height of the cross section and increases the load on the panel and usually have an excess cross-sectional area. Bulb angle bars are widely used in the structure of metal fuselages of airplanes and helicopters, in the tail boom of helicopters, in the wing and tail unit of light aircraft, in flaps, ailerons and rudders. However, modern the bulb angle bar have a significant drawback.When a bulb angle bar is loaded by a transverse load from the skin in the wing structure, tail unit, fuselage, except of normal stresses from bending of the stringer with attached skin, supported by ribs or frames, additional normal and shear torsional stresses arise. This torsion is caused by the fact that the lateral load is not applied at the center of the bend. Additional stresses reduce the service life and tightness of the structure in this place. An altered cross-sectional shape of the bulb is proposed for use in light aircraft panels to increase their strength and service life. The change in shape had a significant impact on the location of the center of the bend in the cross section. The determination of the position of the center of the bend in the balloncube was carried out using the Wagner model with walls not working for shear stresses. The modified cross-sectional shape of the bulbogon allowed to reduce the level of residual stresses after the panels were assembled, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly in the panels. It is recommended to drill holes for rivets in the stringer in the middle of the entire width of its shelf, taking into account the wall.A modified cross-sectional shape of a corner with bulb is proposed for use in light aircraft panels. The change in shape had a significant impact on the location of the center of the bend in the cross section. This made it possible to reduce the level of residual stresses after the assembly of the panels, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly.

Design of knee support device based on four-bar linkage and hydraulic artificial muscle

One of the main challenges for the elderly is insufficient lower limb strength during sit-to-stand movement, which may be improved by supporting the joint externally. Existing lower extremity exoskeletons use perfect revolute joints as knee joints, which do not match with human joint biomechanics. They also require a complex control system to produce the required torque at the corresponding joint angle. In this study, a knee support device using four-bar joint mechanism and hydraulic artificial muscle (HAM) was designed. A previously proposed four-bar linkage joint was modified to accommodate the HAM. In addition, the Angled Bar was proposed to exploit HAM’s force-contraction relationship to generate the desired torque at the corresponding angle only by applying constant hydraulic pressure without the use of a complex control system. The device was able to generate a maximum output of 126.55 Nm torque at 100^{circ } knee joint angle during loading and 70.69 Nm torque at 100^{circ } during unloading at 3 MPa pressure. The root-mean-square error of the knee extension torque curve was 13.01 Nm. Experiment with a healthy participant showed significant reduction in muscle activity with the assist from the device. The maximum processed EMG signal with and without assist were 52.10 and 20.93 {upmu mathrm{V}}, respectively.

Clearance measurement for general steel waste

A large amount of general steel waste is generated during decommissioning and dismantling of nuclear facilities. Very low contaminated radioactive waste, whose radioactivity is below clearance level, generated from the demolition process may be reused for general use. We examined the feasibility of the clearance verification system for uranium waste. The relative error of uranium determination was within 30 % for 1 g of uranium when measuring steel materials (angle bar, channel steel, pipe steel, square steel tube, fragments of steel tube).

Fish guidance structures: hydraulic performance and fish guidance efficiencies

The hydraulic performance and fish guidance efficiency (FGE) for behaviourally-based mechanical fish guidance structures, i.e. louvers and modified angled bar racks (MBRs), were evaluated experimentally and the results are presented herein. Detailed velocity profiling was conducted to assess the hydraulic performance of the 1:1 Froude-scaled racks in an etho-hydraulic laboratory flume. Guidance efficiencies of the studied rack configurations were evaluated through live-fish tests in the same flume. Tests were conducted with five European fish species, namely, barbel (Barbus barbus), spirlin (Alburnoides bipunctatus), European grayling (Thymallus thymallus), European eel (Anguilla anguilla) and brown trout (Salmo trutta). The results demonstrate that MBRs are advantageous over louvers because of reduced head losses, improved hydraulics and higher FGEs. Furthermore, use of a bottom overlay on the MBRs substantially increased the FGE. The results are discussed and compared with literature data. Recommendations for an optimized and economic MBR design are given. The present findings underpin the follow-up studies for further optimization of MBR design.

Hydraulic performance of fish guidance structures with curved bars – Part 1: head loss assessment

The hydraulic performance of fish guidance structures such as louvres and angled bar racks is an important design criterion to achieve high fish guidance efficiencies with a minimum impact on hydropower production. The current geometrical designs of such structures result in high head losses and asymmetric turbine admission flow and hence need to be optimized. We therefore developed an innovative curved bar design for fish guidance structures and experimentally investigated different rack configurations in a laboratory flume. The present paper (Part I) focuses on the hydraulic performance of the novel curved-bar racks with regard to head losses, while in the companion paper (Part II) we report the results on the flow fields. The effects of the main rack angle, bar angle, bar spacing, bar depth, and top or/and bottom overlays were systematically studied. The curved bar shape leads to significantly lower head losses compared to straight bar shapes. An existing head loss prediction formula was extended to account for the new bar shape and the application of overlays.

EFFICIENCY ESTIMATION OF THE SHAPED HOT ROLLED STEEL PRODUCT MIX OF INDIA AND UKRAINE

The publication presents main results of the performed quantitative and qualitative analysis of modern shaped rolled metal products of India, which is used for structural steel members. Its efficiency was compared to the current domestic product range of Ukraine on the example of angle bars, channel sections and flanged beams. Special attention is paid to the system of designations and marking of product mix items. The publication presents the main results of the quantitative and qualitative analysis of the modern hot rolled steel assortment of India, which is used for steel building structures. The shaped hot rolled steel products are considered, represented in the standards of both countries by four types of profiles – equal leg angles, unequal leg angles, channel and beams. Special attention is paid to the system of designations and labeling of products of the assortment. In general, it should be noted that the overall organization and principle of construction of the analyzed assortments of India and Ukraine are quite similar. The main fundamental difference is the availability in the standard of India of a wider range of profile varieties within one step, which makes it possible to more efficiently choose the required section in the design. However, the step itself is widely than in domestic standards, which negates such dignity. Angels profiles in the Indian assortment have a wider range of thicknesses and are represented by a large number of sizes, especially for unequal leg angles, which is connected with a significant distribution of such profiles in the supporting elements of steel structures. Channel profiles in general have approximately the same degree of efficiency and the number of standard sizes in the assortments of both countries. In the standard of India, profiles with flange slopped shelves are displayed in more way and, in the domestic standard, with parallel shelves. Beam profiles have the largest number of sizes in both assortments, but unlike the domestic standard in India's standard, they are presented only in cross-sections with flange slopped shelves. In this case, the profiles aimed at bending, according to the domestic assortment have specific characteristics averaged on 15 – 40 % higher with a less on 30 – 40 % by weight. For profiles of heavy series, oriented also on the perception of longitudinal forces, sections in the Indian assortment have higher specific characteristics and less weight on average by 20 – 30 %.

Thor – a New Design of Overhead Transmission Line Towers

ABSTRACTIn these years Denmark puts a significant effort into reducing the CO2‐emission. Consequently, a more flexible and strong electricity transmission grid is needed to be able to transmit the power from the offshore wind farms to the consumers. Furthermore, the grid must be able to reach the international markets.Therefore, a new detailed design of a series of overhead line (OHL) towers have been carried out. The contemporary design has been prepared by the engineers, Ramboll, together with architects, Dissing+Weitling, for the Danish transmission system operator (TSO), Energinet, and the main purpose is to have an aesthetic OHL acceptable to the public together with a cost‐efficient series of towers.The towers are designed as lattice structures. All the traditional lattice OHL towers are constructed using angle bars, while the new design is constructed of circular tubes for all lattice members. This design gives a more open appearance of the tower that is not as massive as the resent designed OHL towers with a shaft of monopoles. The tubes have multiple advantages compared to angle bars: smaller width, lower wind resistance, higher buckling capacity and wider profile opportunities.The traditional angle bar towers are prepared as almost fully bolted structures with no welding. However, even though the members are bolted together welding must be done on lattice towers of circular tubes, and new connections have been developed; also, to meet the aesthetic requirements.This paper introduces the new transmission line design with focus on the tower structure and the special aesthetic designed connections.

Производство пиломатериалов для строительства из круглых лесоматериалов с ядровой гнилью

Coniferous lumber is popular in low-rise wooden house construction. However, the condition of round timber for lumber production has been going down in recent years. Timber with heart rot is very common nowadays. As a rule, the heart rot removal occurs in harvesting of round timber. At the same time, disease-free sap wood is removed together with the wood affected by the rot in timber cutting. Therefore, a large amount of sound timber remains in forest. Cutting of timber with rot reduces the yield of lumber for construction, as far as rot’s presence in building structures is not allowed. A method of cutting round timber with heart rot is proposed for the purposes of production I-beams from solid wood. It is necessary to know the form and sizes of rot for high-quality rough ripping of round timber with heart rot. The relationship between the cross-sectional dimensions of round timber and heart rot along the length of assortments is quite accurately described by the equations of correlative (allometric) growth. The schemes of cutting round timber with heart rot have been developed taking into account these dependencies. Cutting was carried out by split-pith sawing scheme. Firstly, two four-side edged cants with heart rot in the central part of one of the cross-section layers were produced. Then the beams were longitudinally divided into two parts. Rot was removed from these parts by milling. Angle bars for I-beams production were obtained as a result of conditional cutting of pine round timber. The studies of the I-beam made of angle bars were carried out. The calculated stresses of beam bending do not exceed the accepted values. The useful output of such bars made of round timber with heart rot is calculated. It has been found that the method of manufacturing elements of building constructions from round timber with heart rot will allow to use them in low-rise wooden house construction. This will expand the wood resources for construction.For citation: Toropov A.S., Byzov V.E., Toropov S.A. Lumber Production for Construction from Round Timber with Heart Rot. Lesnoy Zhurnal [Forestry Journal], 2019, no. 4, pp. 133–145. DOI: 10.17238/issn0536-1036.2019.4.133

Experimental performance evaluation of a modified solar still integrated with a cooling system and external flat-plate reflectors

This study was done to improve the productivity of an inclined solar still through some modifications include installing angle bars on the basin to increase the water residence time, fabricating the basin with adjustable inclination angle to achieve the highest amount of solar radiation in each season, installing top and bottom flat-plate external reflectors and a cooling system on the glass cover. The effect of the basin inclination angle, feeding water flow rate, cooling water flow on the glass cover, installing top and bottom reflectors at their optimum inclination angles on the productivity of the still were experimentally investigated under the climatic conditions of Tehran (35°N Latitude and 51°E Longitude) during summer, winter and spring. The results showed that in the case of applying only one modification, passing the cooling water on the glass cover has the most effect on productivity enhancement in spring while applying top reflector at its optimum inclination angle gave the best results in winter. Also, the maximum productivity of 4.2 kg/m2 was obtained for a basin inclined at 25° with top and bottom reflectors inclined at 10° and 45°, respectively. In this case, the feed water and cooling water flow rates were equal to 90 and 720 ml/min, respectively in solar radiation of 800 W/m2, air temperature of 22.5 °C, and wind velocity of 2.4 m/s. Moreover, the efficiency of the still was obtained as 36.7%, which was 14.2% higher than that of the still at an optimum inclination angle of 25° without reflectors and cooling water under the same weather conditions.

Design of filler and compactor for oyster mushroom growing medium (baglog)

Oyster mushroom cultivation requires good quality growing medium (baglog). In addition to good baglog material, a suitable density level is needed for mushroom growth. Filling and compaction of baglog is often found use manual methods so it takes longer time. The objective of this study is to design a filler and compactor mechanical device for mushroom growing medium. The design obtained dimensions of length 150 cm, width 90 cm and height 153.06 cm. The device is operated by an electric motor of 1 Hp with rotation of 1450 rpm. The device capacity is 180 baglog/hour. The design test showed that the material for the main frame component consist of angle bar with size of 40 mm x 40 mm and thickness of 4 mm, was able to load the device with minimum safety factor of 3.58.

Damage assessment on frame structure with bolted joints based on experimental modal analysis

Bolted joint commonly being used as a mechanical joint to connect two or more mechanical components which bring an interest to this study. The complexity of joint element plays an important role in the dynamic investigation. Structural damage happens and often it’s too late to react to it and early detection of structure failure (damage) is beneficial. This paper aims to study the differences between undamaged and damage frame structure with bolted joints. Frame structure consists of 4 angle bar and 16 flat bars fabricated with stainless steel material is used. Total of 32 pcs of M6 screw and nuts are used together with structure. Damage often alter the mode shapes and reduce the natural frequencies. Natural frequencies and mode shapes of both undamaged and damaged data obtained by experimental modal analysis is correlated. Frequency drop is observed on natural frequencies after being correlated and as well as the mode shapes changed occurs on the undamaged and damages structure. Frame structure with damage on the joints able to detect the frequency drops and alter the modes shapes.

Development of a front-end loader for an MTZ tractor using 3D modeling

The paper deals with the design of a front loader using three-dimensional modeling, and its manufacturing. The area of use of the front loader is individual farms with a small but regular need for the volume of transported goods. The existing loaders have greater productivity and correspondingly high cost, which is not suitable for individual farms. The task is to design a simple and reliable front loader that can be aggregated with an MTZ tractor. The loader must have a maximum load capacity of 1000 kg with a safety factor of 2...2,5. The front loader was designed and manufactured. The design was carried out in a three-dimensional CAD software SolidWorks, the calculation of the maximum load was made by the finite element method. During calculations, the optimal geometrical parameters of the loader parts, capable of withstanding a given load with minimum stresses, were determined. The kinematics of assemblies and parts were made and tested allowing the structure to perform its functionality correctly along a given trajectory. The front loader was made on the basis of an individual farm. The available materials for the production of this loader were: channel, pipe, angle bars, 40 mm thick solid metal and standard units - hydraulic cylinders and high pressure hoses. Tests for loading logs have shown that the device is reliable and has good performance. No complaints and comments on the work of the loader were noted. The measures to improve the loader are outlined. These are the development of a rotary assembly of a vertical stand, reinforcement of the boom anchoring axis, development of tractor stoppers. This will allow mobile work with a load of more than 1000 kg.

Design and development of a power groundnut sheller

In Bangladesh groundnut shelling is done manually which is laborious, time consuming and costly. Shelling of groundnut pod with the help of mechanical power can be a probable solution of this problem. A power groundnut sheller was designed and fabricated in Farm Machinery and Postharvest Process Engineering (FMPE) Division, Bangladesh Agricultural Research Institute (BARI), Gazipur during 2011-13. The sheller was made of Mild Steel (MS) angle bar, MS flat bar, MS rod, MS sheet, MS sieve, rubber pad etc. The shelling capacities of power groundnut sheller were 110 and 115 kg/h for Dhaka-1 and BARI Badam-8, respectively. Average breakage of groundnut kernel was 2% at 7.5% moisture content (wb). The maximum and minimum unshelled pods were about12.4% and 9.18% for Dhaka -1 and BARI Badam-8, respectively. The shelling efficiency of the power groundnut sheller for Dhaka-1 and BARI Badam-8 were 86.6 and 88.82% respectively at 11.5% moisture content (wb). Winnowing efficiency was found to be 99% in the power groundnut sheller. The use of power groundnut sheller can reduce the cost of shelling by 76% over the manual groundnut sheller. This power groundnut sheller is recommended for shelling of groundnut at farm level and small industry level in Bangladesh.Bangladesh J. Agril. Res. 43(4): 631-645, December 2018